A lone gunman killed eight people and wounded five others before taking his own life in Omaha, Nebraska, yesterday, the worst shooting in the US since the Virginia Tech massacre earlier this year that left 33 dead.

The killer, armed with a rifle, went on a rampage in a mall busy with Christmas shoppers. Two of the wounded were in a critical condition last night.

The shooter opened fire in Westroads mall, with most killed in the Van Maur department store. Shoppers and staff ran through the mall in panic when he began firing, heading for the exits or barricading themselves in dressing rooms.

According to a local television station, police were investigating what could have been a suicide note left by a 19-year old that was found in the mall. He said he was going out in style.

Witnesses reported hearing as many as two dozen gunshots. They said they heard a series of rapid shots and initially thought it was construction work. Panic set in as people realised it was gunfire and rushed to the exits.

He shot some at point blank and others from a third-floor balcony.

A woman who saw him rush past said: "It was just crazy." She helped a woman and her child, and they hid in a backroom. She described the killer's behaviour as bizarre, including shooting the stuffing out of a teddy bear.

Jeffrey Peck, manager of a leather goods store, said mall workers ran up to tell him to close up his store. "I told the customer to go into the back room and, as I was shutting the gate, I heard two gunshots ring out," he said.

Some of those shot were waiting in line to get Christmas presents wrapped at Von Maur.

The police were alerted in a 911 call in which shots could be heard in the background. The police response time was six minutes, slow by US standards, but Sergeant Teresa Negron said that every police officer in the city was immediately dispatched to the spot. "We do not believe that we have any other shooter," she told reporters. "The person we believe to be the shooter has died of a self-inflicted gunshot wound."

President George Bush had been on a visit to Omaha yesterday to help raise funds for a local Republican congressional candidate. He left the city an hour before the shooting.

The killing is unlikely to result in a review of US gun laws. The Virginia Tech massacre failed to provoke a serious national debate, and gun laws are, in the main, not an issue in the presidential campaign, with none of the candidates proposing reform.

In October 2006, a milk truck driver tied up and shot 10 Amish schoolgirls in their classroom in Pennsylvania, killing five of them before turning the gun on himself. Such incidents create, for the most part, only short bursts of introspection.

The supreme court is to rule next year on the constitutional right to bear arms. The court is looking at whether states, or Washington DC, have a right to restrict possession of guns: handguns are banned in the District of Columbia. But the supreme court will not overturn the right of an individual to possess a firearm.

The gunman was found dead on the third floor of the Von Maur department store. Police identified him and headed immediately for his home to hunt for clues as to motive.

A witness, Shawn Vidlak, said he heard four or five rapid shots "like a nail gun". At first he thought it was noise from construction work going on at the mall. People started screaming about gunshots. I grabbed my wife and kids we got out of there as fast as we could."

Keith Fidler, a Von Maur employee, said he heard a burst of five to six shots followed by 15 to 20 more rounds. Fidler said he huddled in the corner of the men's clothing department with about a dozen other employees until police yelled to get out of the store.

Kevin Kleine, 29, who was shopping with her 4-year-old daughter, said she hid in a dressing room with four other shoppers and an employee.

"My knees rocked. I didn't know what to do, so I just ran with everybody else," Kleine said.